LONDONDERRY/DERRY, Northern Ireland - Two teenage youths, one 18, and the other 19, have been arrested over the murder of popular Belfast journalist Lyra McKee, who was shot to death in the Creggan area of Derry on Thursday night.

Police are treating the murder as an act of terrorism, and suspect the new IRA are behind it.

"This morning we arrested two teenagers, aged 18 and 19, under the Terrorism Act and conducted a number of searches as part of the ongoing investigation into Lyra’s murder. Both males have been taken to Musgrave Serious Crime Suite," Detective Superintendent Jason Murphy, the senior detective handling the case told media on Saturday afternoon.

"I’ve just come from a very difficult meeting with Lyra McKee’s family and her partner and, as you can imagine, they are absolutely devastated."

"Lyra’s family have a lot of questions, and I answered as many for them as I can at this stage but I need more help from the community to answer all their questions and to bring those who killed Lyra to justice," Murphy said.

"Shortly before 11pm on Thursday night, 29 year old Lyra was murdered by terrorists. I believe that the people responsible are members of the new IRA."

"Lyra was killed by shots that were fired indiscriminately in Fanad Drive. The brutal nature of the attack has sent shockwaves around the world. The shots were fired in a residential area at a time when there were large numbers of local people on the street including children. The gunman showed no thought for who may have been killed or injured when he fired these shots," the detective superintendent said.

"This afternoon, I have a number of specific appeals to make."

"I know that a large number of people were in the area of Fanad Drive and Central Drive on Thursday night. Many of these people were clearly using their phones to video events and will have imagery which may be vitally important," Murphy said.

"Please come and speak with my detectives and provide us with your mobile phone footage. We do not need to hold on to your phone, we have necessary equipment that will allow us to download the footage quickly. Alternatively, you can use the Major Incident Public Portal at www.MIPP.police.uk to upload footage or to tell us what they know."

"I know there will be some people who know what happened but are scared to come forward." the PSNI official said.

"I want to reassure you that we will work with you sensitively. There is a sense that what happened to Lyra marked a sea-change and I want people to have the confidence to come forward and help us. Those who killed Lyra in this cowardly attack must not be allowed to do this again."

"The individuals responsible for Lyra’s murder continue to hide in the shadows, attempting to justify their actions to each other. They have shown no courage to offer any explanation directly to Lyra’s family. Meanwhile the community continue to work together with local policing to bring a lasting and positive change for the community of the Creggan. This should be Lyra’s legacy," Murphy said.

"Lyra’s murder was not just an attack on Lyra - it was an attack on the fabric of the community. Lyra’s killers have succeeded only in uniting the entire community in condemnation."

"If you have information, no matter how small, please contact detectives in the incident room on 101 or via the Crimestoppers charity."